Physicochemical features, metal availability and enzyme activity in heavy metal-polluted soil remediated by biochar and compost

Potential of pigeon pea [Cajanus cajan (L.) Millsp.] associated with endophytic bacterium Bacillus cereus PEB-9 to remediate cadmium-contaminated soil

Phytoremediation associated with plant-beneficial bacteria has gained considerable attention for its efficiency in remediating cadmium (Cd)-contaminated soil. In this study, we isolated an endophytic bacterium, PEB-9, from pigeon pea, which was identified as Bacillus cereus and exhibited strong plant growth-promoting traits along with high Cd resistance in vitro. Pot experiments demonstrated that PEB-9 inoculation increased in pigeon pea biomass (11.45-19.29 %), Cd accumulation (43.89-69.90 %), and the Cd transfer factor (4.17-16.89 %) in Cd-stress soil (2-10 mg/kg), with soil remediation efficiency improving by 11.1-15.4 %. Under Cd stress, PEB-9-treated pigeon pea exhibited significant improvement in the activities of superoxide dismutase, peroxidase, and catalase, while a notable decrease in malondialdehyde content, indicating a reduction in Cd cytotoxicity. Additionally, the chlorophyll content in PEB-9-treated plants was significantly higher than that in the control group. Furthermore, PEB-9 inoculation enhanced bioavailable Cd, soil enzymes activity and nutrient content, including available nitrogen, phosphorus, and organic matter, while also boosting the relative abundance of stress-resistant bacterial groups, such as Proteobacteria and Actinobacteria. Correlation analysis indicated that soil nutrient changes induced by PEB-9 significantly influenced bacterial community structure, thereby regulating plant physiological responses, and improving Cd remediation efficacy of pigeon pea. These findings offer a valuable basis for the practical implementation of PEB-9 in remediating Cd-contaminated soils.

The restoration of zinc pollution in smelting site soil using nanohydroxyapatite-modified cyanobacterial biochar and its mechanism

Heavy metal pollution in the soils at smelting sites must be effectively controlled. Recent advancements in stabilization technology have shown promising results in the remediation of heavy metal-contaminated soils. In this study, nanohydroxyapatite (nHAP) and cyanobacterial biochar were co-pyrolyzed to produce nHAP-modified cyanobacterial biochar (nHAP-CBC), which was applied to remediate Zn contamination of soils at smelting sites. The remediation effect of nHAP-CBC on Zn-contaminated soil was evaluated using batch experiments, and the materials were characterized using XRD, SEM, TEM, BET, and FTIR. These analyses confirmed the uniform dispersion of nHAP on the CBC to form a stable nHAP-CBC material. The results demonstrated that nHAP-CBC effectively converted Zn from an unstable state to a stable state, achieving a 65.79 % conversion rate and a 64.24 % stabilization rate during toxicity characteristic leaching after 45 days of treatment. nHAP-CBC was the most effective at fixing Zn and significantly increased the organic matter (OM) content, suggesting that OM played a key role in Zn fixation. In conclusion, the nHAP-CBC developed in this study can effectively stabilize heavy metals in smelting site soils and offers promising potential for expanding cyanobacterial resource utilization.

Stabilization effects and mechanisms of lignin-based hydrogel-coated sulfide nano-zero-valent iron on lead and cadmium contamination in soil

Nano zero-valent iron (nZVI) is extensively employed in soil remediation due to its superior capacity for removing heavy metals, however, issues related to its agglomeration and oxidation hinder its practical application. Therefore, in this study, lignin-based hydrogel-coated nano ferric sulfide (BLS-nZVI@LH) was synthesized and evaluated for its stabilizing effect, underlying mechanism, and influence on the soil microenvironment and health risks. The results indicate that BLS-nZVI@LH significantly mitigated nZVI agglomeration and oxidation, thereby enhancing its reactivity. The formation of FeS on the particle surface provided additional active sites for stabilizing Pb and Cd in the soil. In soil incubation experiments, BLS-nZVI@LH significantly improved the stability of Pb and Cd after 90 days. Compared to sulfide nano-zero-valent iron (S-nZVI) and ball-milled lignin sulfide nano-zero-valent iron (BLS-nZVI), BLS-nZVI@LH increased the soil's residual Cd content by 23.0 % and 31.0 %, respectively, and the oxidizable Pb content by 10.9 % and 20.8 %. Characterization analysis revealed that precipitation, redox reactions, and surface complexation primarily govern Cd stabilization by BLS-nZVI@LH, whereas complexation and reduction predominantly contribute to Pb immobilization. Furthermore, BLS-nZVI@LH improved soil pH and organic carbon content, boosting β-glucosidase and peroxidase activities. It also promoted the richness and diversity of soil microbial communities, particularly enhancing the growth of Sphingomonas, Gemmatimonas, and RB41, thereby improving the soil microenvironment and boosting remediation capacity. In continuous cropping experiments, the addition of 0.5 % and 1 % BLS-nZVI@LH significantly reduced Pb and Cd absorption and accumulation in Chinese broccoli. Notably, 1 % supplementation lowered Pb and Cd levels in edible parts below the national food safety standard (Pb ＜ 0.3, Cd ＜ 0.2 mg·kg-1), thereby effectively mitigating dietary health risks across different populations. This study offers technical insights into the development of highly active modified materials and provides scientific evidence for the application of BLS-nZVI@LH in stabilizing Pb and Cd contamination in soils, improving soil health, and reducing heavy metal accumulation in crops.

Geographical variation, accumulation risk, and risk management of rice heavy metal(loid) contamination in China

Grain is a crucial source of human nutrition, and its quality is linked to the health of populations and sustainable development of economies and societies worldwide. However, at national and global scales, information on rice quality and safety is relatively limited. To address this knowledge gap, this study constructed a high-resolution nationwide database of heavy metal (HM) pollution in rice across major grain-producing areas in China based on extensive field survey data from 2018 to 2020 (3198 samples). The database was used to evaluate the pollution status, identify hotspot distribution areas, and supplement existing knowledge gaps. The results revealed that the mean concentrations of HM in rice exceeded the standard value in varying degrees across provinces, with Cd, Pb, and Hg being the most prominent pollutants, showing exceedance rates of 18.7 %, 6.4 %, and 4.2 % respectively. Hotspot analysis indicated that the spatial aggregation of HM contaminations was significantly influenced by human activities, with pollution primarily concentrated in industrial and mining clusters or economically developed regions. Moreover, the consumption of contaminated rice poses both carcinogenic risks (eg., Cd, As, or Ni) and non-carcinogenic hazards to human health. These findings highlight the urgent need for action from the government to implement green restoration strategies for HM-contaminated rice.

Potential impacts of polyethylene microplastics and heavy metals on Bidens pilosa L. growth: Shifts in root-associated endophyte microbial communities

This study investigates the impact of polyethylene (PE) microplastics of varying particle sizes and concentrations on the growth of Bidens pilosa L. and its root-associated microbial communities in cadmium (Cd) and lead (Pb) co-contaminated soil. PE microplastics had a significant impact on plant growth. Notably, at the P05-10 level, root length, root weight, and total biomass exhibited the greatest reductions by 48.9 %, 44.1 %, and 45.2 %, respectively. Furthermore, PE microplastics reduced photosynthetic pigment levels and promoted the accumulation of reactive oxygen species, as indicated by a 264.8 % and 57.2 % increase in H2O2 content in roots and leaves. High-throughput sequencing revealed substantial alterations in the composition of bacterial and fungal communities, with stress-resilient taxa such as Actinobacteria, Verrucomicrobiota, and Rhizophagus exhibiting increased relative abundance. Correlation analyses indicated that variations in soil pH and enzymatic activity influenced microbial community structure, which in turn affected plant physiological responses. Functional predictions using PICRUSt2 and BugBase suggested enhanced oxidative stress tolerance, increased secondary metabolite biosynthesis, and a higher prevalence of stress-resistant phenotypes under conditions of elevated PE concentrations and smaller particle sizes. Overall, this study provides novel insights into the potential effects of microplastics on Bidens pilosa L., particularly in its role as a hyperaccumulator, highlighting its capacity for heavy metal uptake under microplastic exposure.

Soil pH and total phosphorus regulate bacterial community assembly in slope restoration areas of the Tibetan Plateau's metal mining areas

Microbial community development is a crucial aspect of soil restoration. The employment of frame beams in conjunction with external soil has demonstrated efficacy in the rehabilitation of degraded roadside ecosystems within mining regions. Nonetheless, the effects of frame beams on the composition and stability of soil bacterial communities remain inadequately comprehended. We conducted a one-time soil sampling on a three-year restored slope in a large-scale metal mining area on the Tibetan Plateau, providing a snapshot of the current conditions and evaluating the restoration progress. Frame beams with external soil covers were applied at three different altitudes: A1 (4800-5000 m), A2 (4500-4700 m), and A3 (4200-4400 m). Restoration significantly altered bacterial community composition compared with controls. Proteobacteria had a higher relative abundance in the restoration area (average: 31.16 %), whereas Acidobacteriota were more abundant in the control area (average: 24.68 %). In the restoration area, soil bacterial α-diversity increased as elevation decreased, with the Shannon index rising from 5.34 (A1) to 5.82 (A3), suggesting that bacterial communities at higher altitudes are more sensitive to environmental conditions. Species turnover was the primary driving factor of β-diversity, accounting for 96.26 % under A1, 94.71 % under A2, and 91.94 % under A3, respectively. The nearest taxon index of bacterial communities shifted from negative to positive along the elevation gradient (-0.25 to 1.14), indicating an increasing trend toward community clustering. Within the bacterial co-occurrence network, soil pH and total phosphorus contribute significantly to network strength, closeness, and betweenness. Concluding, soil pH and total phosphorus were identified as key factors shaping bacterial diversity and assembly mechanisms. Our research contributes to the development of effective soil restoration strategies for alpine mining regions, providing insights into microbial community assembly and stability mechanisms.

Strategy for enhanced soil lead passivation and mitigating lead toxicity to plants by biochar-based microbial agents

In the study, bone char (BC) backed biochemical composite coupling with phosphate-solubilizing bacteria (CFB1-P) was prepared to explore the passivation performance of lead (Pb) in soil and the mitigation effect on plant growth under Pb stress by measuring change of soil Pb speciation, plant growth parameters and physiological and biochemical indexes. After 30 d of remediation, addition of 1 % CFB1-P could effectively reduce 55.43 % of Pb labile fractions and converted them into Fe-Mn oxide and residual forms. Meanwhile, the bioavailability of Pb was not significantly affected by wetting-drying and freezing-thawing after 20 times cycles (the DTPA-Pb content only increased 6.91-7.35 mg/kg), which proved that the CFB1-P had an excellent prospect of passivating Pb. Moreover, the CFB1-P effectively increased soil fertility and improved soil enzyme activity. The application of CFB1-P could reshape the soil microbial community by recruiting beneficial microorganisms (Bacillus, Sulfurifustis, and Gaiella), which contributed to the improvement of Pb-contaminated soil quality. Furthermore, the fresh weight, photosynthetic pigment concentration, stems and roots length of cucumber seedings were significantly increased. Pb in the cucumber seedings and antioxidant enzyme activities of cucumber seedings were prominently decreased. Therefore, the study can offer a preferable comprehending for the advance of sustainable high-efficiency materials which microbial agent based on functional biochar remediated Pb-polluted soil.

Remediating heavy metal-contaminated soil through invasive alien plant-derived biochar and stinging nettle powder

Invasive alien plant species (IAPS) threaten ecosystem integrity worldwide. IAPS eradication is expensive, and their biomass is considered waste. Producing biochar from IAPS biomasses could turn waste into a resource. At the same time, this material could be used to remediate polluted soils. Also, using widespread native weeds, such as Urtica dioica (U), as an additional amendment could further improve soil remediation. In a phytoremediation experiment, we applied biochar produced from two widespread IAPS' biomass, i.e. Ailanthus altissima (Mill.) (BA) and Solidago gigantea Aiton (BS), at different rates (2 % and 5 % w/w) together with Urtica dioica L. powder (U) (2 % w/w) in an Arsenic (As) and Lead (Pb)-contaminated soil, using Phaseolus vulgaris L. as an indicator plant species. We measured the amendment's effects on soil pore water (SPW) properties, plant and fine root development, and soil enzymatic activities. When BS was added alone, and when BA was combined with U SPW's pH and electrical conductivity (EC) increased and [Pb] diminished, which augmented plant growth and reduced Pb uptake. Combining the biochar types and U increased the soil's enzymatic activities, fine root length, biomass, and specific root length. Finally, both biochar types with U increased As mobility in SPW, leading to higher plant uptake in roots, although without translocation to aboveground organs. Our findings contribute to developing cost-effective and environmentally sustainable practices for managing polluted soil. Simultaneously, they tackle the problem of IAPS, which can be used in the future to provide guidelines for policymakers.

Collaborative effects of antimony-arsenic contaminations on microbial communities in the typical antimony mining areas of Southwest China

Antimony (Sb) and arsenic (As) co-contamination is prevalent in Sb mining areas and poses significant risks to the surrounding ecological environment. However, the extent of this co-contamination and the impact of key environmental variables and long-term exposure on the microbial communities remain poorly understood. Therefore, this study assessed Sb-As levels in three representative antimony mining areas in Southwest China and explored the relationships between microorganisms and environmental variables. The results indicated that the concentrations of soil Sb ranged from 6.90 to 50,794.07 mg/kg and As from 4.56 to 8798.86 mg/kg. The potential ecological risk index (RI) in mining and smelting areas surpassed 260, indicating a significantly high risk level. Sb-As predominantly exist as residual fractions. pH, electrical conductivity (EC), and interactions between Sb-As are critical factors influencing the transformation of their chemical fractions. Sb-As exposure altered the microbial community structure and diversity, with positive correlations dominating the co-network. Spearman correlation, redundancy analysis (RDA), canonical correspondence analysis (CCA), and random forest analysis (RF) indicated that the total concentration of Sb-As, the bioavailable fractions of Sb-As, pH, oxidation-reduction potential (Eh), and EC were the main variables affecting the microbial community. Variation partition analysis (VPA) indicated that Sb-As and their chemical fractions explained more microbial community variation than the physicochemical properties. Moreover, the bioavailable fractions were an even more significant variable influencing the microbial communities than the total concentrations of Sb-As. In-depth research on the ecological impact of Sb-As on microbial communities provides valuable insights for environmental monitoring and management.

Divergent altitudinal patterns of arbuscular and ectomycorrhizal fungal communities in a mid-subtropical mountain ecosystem

Arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) form ubiquitous symbiotic relationships with plants through co-evolutionary processes, providing multiple benefits for plant growth, productivity, health, and stress mitigation. Mountain ecosystem multifunctionality is significantly influenced by mycorrhizal responses to climate change, highlighting the importance of understanding the complex interactions between these fungi and environmental variables. In this study, we investigated five vegetation zones across an altitudinal gradient (675-2157 m a.s.l.) in Wuyi Mountain, one of the most well-preserved mid-subtropical mountain ecosystems in eastern China. Using high-throughput sequencing, we examined the altitudinal distribution patterns, community assembly mechanisms, and network interactions of soil AMF and EMF. Our analyses demonstrated significant altitudinal variations in the composition and diversity of mycorrhizal fungal communities. AMF richness peaked in the subalpine dwarf forest at intermediate elevations, whereas EMF richness was highest in the low-altitude evergreen broad-leaved forest, showing a marked decrease in the alpine meadow ecosystem. β-diversity decomposition revealed that species turnover constituted the primary mechanism of community differentiation for both fungal types, explaining >56% of the observed variation. Stochastic processes dominated community assembly, with the relative importance of dispersal limitation and drift showing distinct altitudinal patterns. Network analysis indicated that AMF networks reached maximum complexity in evergreen broad-leaved forests, while EMF networks showed similar complexity levels in coniferous forests. Among the examined factors, soil properties emerged as the predominant driver of altitudinal variations in ecosystem multifunctionality, followed by AMF communities and climatic variables. These findings provide critical insights into the ecological functions and environmental adaptations of mycorrhizal fungi, advancing our understanding of their responses to environmental changes in mountain ecosystems and informing evidence-based conservation strategies.

Green remediation of REEs-contaminated soil by biodegradable chelators with optimization and risk assessment

The omnipresence of rare earth elements (REEs) in the environment, driven by their extensive industrial applications and common occurrence in some weathered crusts, has raised significant concerns as emerging pollutants. Soil washing has been recognized as an effective approach to remediate REEs-contaminated soils. However, traditional washing agents frequently lead to soil acidification and salinization, adversely affecting soil microbial communities and plant growth. This study explored the use of biodegradable chelators (BCs)-specifically N,N-bis(carboxymethyl)-L-glutamic acid (GLDA), iminodisuccinic acid (ISA), and polyaspartic acid (PASP)-as alternatives for removing REEs from contaminated agricultural soils. Our findings demonstrated that the removal efficiency of REEs positively correlates with BCs concentration, liquid-to-solid ratio, and washing time, while showing a negative correlation with solution pH. Through response surface analysis, we determined the optimal parameters for the washing process, revealing that GLDA, ISA, and PASP achieved total REEs removal efficiencies of 50.8%, 40.5%, and 23.2%, respectively. Statistical analysis confirmed that the concentration of BCs was the primary factor influencing washing effectiveness. Moreover, washing with BCs significantly removed reducible REEs-those bound to iron/manganese oxides-thereby decreasing the mobility and bioavailability of REEs in soil. The reduction in bioavailable REEs significantly lowered the environmental risk associated with contaminated soil. Notably, the activity of soil enzymes improved post-washing with BCs, indicating a positive impact on soil health. This study provides valuable insights into the remediation of REEs-contaminated soils using BCs, with GLDA emerging as a particularly effective agent.

Melatonin application enhances the remediation of cadmium-contaminated soils by Cinnamomum camphora

Cinnamomum camphora (C. camphora) is a tolerant plant with high potential for cadmium (Cd) uptake and resistance. However, it is still unclear how melatonin application regulates Cd absorption and detoxification in C. camphora, and whether the soil quality is improved after remediation. In this study, melatonin was applied at the concentration of 20 mg·kg-1 soil to the Cd-contaminated soil planted with C. camphora. We aimed to investigate the effect of exogenous melatonin on Cd phytoextraction and detoxification in C. camphora by assessing physiological and biochemical responses. We found that melatonin application improved Cd content in C. camphora (p < 0.05), with a pronounced increase by 150 % in both stem phloem and leaves. Under Cd stress, melatonin application resulted in a Cd bioconcentration factor that was over 2-times higher, and Cd translocation factors from root to stem and from stem to vein which were increased to the level of 1.0. Exogenous melatonin also enhanced plant growth and photosynthesis under the 180-day Cd stress. In addition, melatonin promoted C. camphora to modify its antioxidant defense systems in response to various temporal stages of Cd stress. At the early stage, melatonin decreased malondialdehyde by >20 % and increased both proline and glutathione reduction by over 30 %. At the late stage, melatonin increased glutathione and soluble sugar by 46.0 % and 10.7 %, respectively. Peroxidase activity was stimulated by melatonin throughout the growth period (p < 0.05). In the remediated soil, melatonin application decreased soil respiration by 12.5 % and inhabited activities of urease, catalase, and dehydrogenase, indicating improved soil quality. Overall, our findings suggest that melatonin application can enhance Cd phytoextraction and detoxification in C. camphora from contaminated soils, providing new insights into applicable strategies for Cd phytoremediation.

Effects of Modified Biochar on Growth, Yield, and Quality of Brassica chinensis L. in Cadmium Contaminated Soils

Cadmium (Cd) pollution in farmland soil leads to excessive Cd in vegetables, which can be transferred to humans through the food chain, posing a significant threat to human health, and requires urgent measures to combat it. Modified biochar may have the potential to remediate Cd pollution in farmland soils. In this experiment, bulk biochar (YC) derived from reed straw or modified biochar by ball milling (Q) either alone or combined with a combination of several passivation agents {potassium hydroxide (K), attapulgite (A), calcium magnesium phosphate fertilizer (M), and polyacrylamide (P)} was applied to soils polluted with Cd, to investigate the growth, yield, and quality of pakchoi (Brassica chinensis L.). The results showed that bulk biochar (YC) provided pakchoi with plenty of nitrogen, phosphorus, and potassium, while passivation agents enhance macronutrient accumulation. Compared to YC, modified biochar improved pakchoi yields and nutritional quality. Among them, concentrations of nitrates in pakchoi significantly decreased by 51.8% and 51.0%, while vitamin C levels increased by 29.6% and 19.0%, respectively, in QKAMP and QKAM treatments. The contents of Cd in pakchoi significantly decreased by 21.6% and 18.6%, respectively, in QKAMP and QKAM treatments. The implementation of QKAMP led to the cadmium contents in edible vegetables being lower than the maximum stipulated content as defined by the national standard, but QKAM failed to accomplish it. In conclusion, QKAMP effectively reduced the bioavailability of Cd in the middle to slightly Cd-polluted alkaline soils, making it a suitable soil amendment to improve the yield and quality and mitigate Cd accumulation in vegetables.

Biochar for ameliorating soil fertility and microbial diversity: From production to action of the black gold

This article evaluated different production strategies, characteristics, and applications of biochar for ameliorating soil fertility and microbial diversity. The biochar production techniques are evolving, indicating that newer methods (including hydrothermal and retort carbonization) operate with minimum temperatures, yet resulting in high yields with significant improvements in different properties, including heating value, oxygen functionality, and carbon content, compared to the traditional methods. It has been found that the temperature, feedstock type, and moisture content play critical roles in the fabrication process. The alkaline nature of biochar is attributed to surface functional groups and addresses soil acidity issues. The porous structure and oxygen-containing functional groups contribute to soil microbial adhesion, affecting soil health and nutrient availability, improving plant root morphology, photosynthetic pigments, enzyme activities, and growth even under salinity stress conditions. The review underscores the potential of biochar to address diverse agricultural challenges, emphasizing the need for further research and application-specific considerations.

Phytoremediation of Oil-Contaminated Soil by Tagetes erecta L. Combined with Biochar and Microbial Agent

Crude oil pollution of soil is an important issue that has serious effects on both the environment and human health. Phytoremediation is a promising approach to cleaning up oil-contaminated soil. In order to facilitate phytoremediation effects for oil-contaminated soil, this study set up a pot experiment to explore the co-application potentiality of Tagetes erecta L. with two other methods: microbial agent and biochar. Results showed that the greatest total petroleum hydrocarbon (TPH) biodegradation (76.60%) occurred in the soil treated with T. erecta, a microbial agent, and biochar; the highest biomass and root activity also occurred in this treatment.GC-MS analysis showed that petroleum hydrocarbon components in the range from C10 to C40 all reduced in different treatments, and intermediate-chain alkanes were preferred by our bioremediation methods. Compared with the treatments with biochar, the chlorophyll fluorescence parameter NPQ_Lss and plant antioxidant enzyme activities significantly decreased in the treatments applied with the microbial agent, while soil enzyme activities, especially oxidoreductase activities, significantly increased. Although the correlation between biochar and most plant growth and soil enzyme activity indicators was not significant in this study, the interaction effect analysis found a synergistic effect between microbial agents and biochar. Overall, this study suggests the co-addition of microbial agents and biochar as an excellent method to improve the phytoremediation effects of oil-contaminated soil and enhances our understanding of the inner mechanism.

Promoting the recovery of soil health in As and Sb-polluted soils: new evidence from the biochar-compost option

The role of compost and biochar in the recovery of As and Sb-polluted soils is poorly investigated, as well as the influence of their application rates on soil health and quality. In this study, we therefore investigated the effectiveness over time (2, 4, and 6 months, M) of a municipal solid waste compost (MSWC) and a biochar (BC), applied at 10 and 30% rates, and of selected mixtures (MIX; applied at 10 and 30% total rates, 1:1 ratio of MSWC and BC), on labile As and Sb in a polluted soil from an abandoned Sb mine (Djebel Hamimat, Algeria). At the same timepoints, the amendment impact on soil chemistry was also monitored, while the activity and diversity of the resident microbial communities were investigated at 6 M. After 6 months, MSWC, BC, and MIX applied at the higher rate significantly increased soil pH (from 7.5 up to 8.2), while MSWC and MIX increased soil EC to worrying values. The soil dissolved organic carbon content was also greatly increased by MSWC and MIX at the higher rates (up to 50-fold), while BC showed a negligible impact. All the amendments reduced the concentration of labile Sb in soil, with BC 10% being the most effective treatment (i.e., reducing labile Sb from ~ 60 to 20 mg kg-1 soil). On the contrary, only BC and MIX applied at 10% significantly reduced labile As (e.g., from ~ 12 to 4 mg kg-1 soil in the case of BC). MSWC and MIX at both rates increased up to 2000-fold soil dehydrogenase activity, while BC showed a null impact. The Biolog community level physiological profile and sequencing of the partial 16S rRNA gene showed a reduction of catabolic activity and α-diversity and a change of the community composition of bacterial populations in treated soils. Overall, MIX treatment, especially at 10%, was the most promising option for the chemical and biological recovery of As and Sb-polluted soils.

Phosphate-enhanced Cd stabilization in soil by sulfur-doped biochar: Reducing Cd phytoavailability and accumulation in Brassica chinensis L. and shaping the microbial community

To explore the potential of livestock manure-derived biochar for the remediation of Cd-contaminated soil, a pot experiment was conducted to explore the stabilization efficiency of cattle manure biochar (T2, BC), sulfur-doped biochar (T3, SBC), and SBC combined with phosphate (T4, SBC-PF) on Cd in contaminated soil and their effects on Cd accumulation in Chinese cabbage (Brassica chinensis L.) and soil microorganisms. The results showed that soil available phosphorus (AP), available potassium (AK), and organic matter (OM) significantly increased in T3 and T4, and the biomass of Chinese cabbage also increased from 0.46 g/pot to 0.57 and 1.05 g/pot, respectively. The DTPA-extractable Cd in T3 and T4 dramatically reduced by 78.6% and 91.4% (p < 0.05); the acid-soluble Cd decreased by 11.3% and 13.2%; and the residual Cd increased by 30.0% and 10.0%. Most importantly, the Cd contents in T2, T3, and T4 decreased by 2.2%, 89.7%, and 93.1% in the shoots of Chinese cabbage and 21.3%, 82.2%, and 86.2% in the roots of Chinese cabbage, respectively. Moreover, SBC-PF obviously changed the bacterial community and enhanced the interactions among microbes in the soil. Structural equation modeling revealed that microbial interspecific mutualistic relationships were the key factor in the pathway for reducing Cd phytoavailability. Mantel tests and random forest analyses further revealed that biochar enhanced the interactions among microorganisms by increasing the AP content in the soil. These findings demonstrated that SBC combined with phosphate is appropriate for stabilizing Cd and improving soil quality.

Effects of Distiller's Grains Biochar and Lactobacillus plantarum on the Remediation of Cd-Pb-Zn-Contaminated Soil and Growth of Sorghum-Sudangrass

Soil contamination with heavy metals is a significant environmental issue that adversely affects plant growth and agricultural productivity. Biochar and microbial inoculants have emerged as a promising approach to solving this problem, and previous studies have focused more on the remediation effects of single types of materials on heavy metal soil pollution. This study examined the impact of both standalone and combined applications of distiller's grains biochar, Lactobacillus plantarum thallus, and the bacterial supernatant on the availability of cadmium (Cd), lead (Pb), and zinc (Zn) in soil, its physicochemical features, and its enzyme activities; this study also examined the growth, physiological and biochemical characteristics, and heavy metal accumulation of Sorghum-sudangrass. The findings suggest that the application of distiller's grains biochar, Lactobacillus plantarum thallus, and the bacterial supernatant can improve the soil's physical and chemical properties and enhance soil enzyme activity while reducing the availability of heavy metals in the soil. Furthermore, the addition of these materials promoted plant growth, increased stress resistance, and significantly decreased the accumulation of heavy metals in the plants. A thorough analysis of the results shows that applying 0.025% Lactobacillus plantarum thallus along with 4.4% distiller's grains biochar produced the best results.

Effect of organic amendments on the alleviation of cadmium in red amaranth (Amaranthus gangeticus) grown in Cd-contaminated saline soils

Cd-contaminated saline soil is now becoming a serious threat affecting sustainable agriculture throughout the world. In this study, organic amendments (OA) were applied to Cd-contaminated saline soils to, firstly, reduce the bioavailability of Cd in soil and, secondly, minimize Cd accumulation in red amaranth (Amaranthus gangeticus) plant. The soil was treated with 1% and 2% of cow dung (CD), vermicompost (VC), waste tea (WT), saw dust (SD), rice hull (RH), and compost. Red amaranth (Amaranthus gangeticus) plant was grown using a pot experiment in control and OA-treated soil stressed with both salinity (4 dsm-1 and 8 dSm-1) and Cd (5 mgkg-1). In slightly saline conditions (4 dSm-1), the addition of 1% CD and VC reduced the bioavailable Cd in the soil to 17.44% and 15.12%, respectively. The reduction increased to 24.42% and 25.58% with 2% rate of application in the same soil. However, in moderately saline soil (8 dSm-1), the reduction varied significantly only with the higher rate. Shoot Cd content was reduced by 85.86% using 2% VC in low saline soil. The bioconcentration factor was also lowered with the addition of CD and VC; however, the performance proved to be better in low saline soil at 2% rate of application. The health risk index (HRI) value for the adults was observed to be < 1 only when the soil with low salinity was treated with 2% VC. Consequently, VC can be used in Cd-contaminated saline soils for red amaranth cultivation to reduce risks to people's health.

Environmental problems of emerging toxic metals and treatment technology and methods

The increasing industrial use of toxic metals essential for modern electronics and renewable energy presents significant environmental and health challenges. This review was needed to address the environmental risks posed by toxic metals, particularly those accumulating in soil and sediment ecosystems. The objective is to examine the sources of toxic metal pollution, their ecological impacts, and the effectiveness of existing treatment technologies. By comprehensively reviewing the recent literature, we analyzed the physiological and molecular responses of plants to toxic metals, focusing on their toxicity mechanisms. Key parameters measured include toxic metal concentration, soil and sediment health, microbial diversity, and plant stress responses. Our findings highlight that toxic metals, such as lithium, nickel, and indium, fueled by industrial activities, including mining and electronic waste disposal, significantly disrupt ecosystems. These metals bioaccumulate, harming soil microbial communities and aquatic life. For instance, in soil ecosystems, cadmium and lead inhibit microbial functions, while in aquatic systems, resuspension of sediment-bound metals leads to persistent contamination. Data show that phytoremediation and microbial techniques are effective in reducing toxic metal concentrations up to 30-40%. In conclusion, long-term monitoring and sustainable remediation strategies are essential to mitigate these environmental impacts. Future efforts should focus on enhancing the efficiency of bioremediation techniques and integrating these methods into global toxic metal management practices.

Toxic metal pollution and associated health risk in nonferrous metal smelting soil containing clay minerals

Given the research situation of toxic metals (TMs) pollution in farmland soil, it is very critical to study the clay influence on TMs environmental behavior to meet the aim of lowering TMs pollution. This research explores the association among clay minerals and TMs and the health risks in TMs combined polluted farmland of northern China. In this study, agricultural soil, wheat grain, and atmospheric sediments from nonferrous metal smelting (NMS) areas were collected and investigated to determine the effect of clay minerals on TMs. The results show that the content ranges of Cd (0.199 mg/kg ∼1.98 × 102 mg/kg), Pb (0.228 × 102 mg/kg ∼ 4.87 × 103 mg/kg), Cu (0.187 × 102 mg/kg ∼ 4.57 × 103 mg/kg), and Zn (0.559 × 102 mg/kg ∼ 3.04 × 103 mg/kg) in the agricultural soil. In particular, Cd has reached heavy pollution by the high pollution index (6.74). The findings indicate that Cd and Pb in wheat grain were influenced by their exchangeable fractions in soil, according to a significant relationship between Cd and Pb in soil and wheat grain. XRD-SEM suggests that TMs come from atmospheric sediments associated with NMS emissions by microsphere signatures with surface burn marks. Meanwhile, Geographical detector indicated that clay was the primary contributor to spatial distribution of Cd and Pb. In addition, XRD results showed that I/S (a mixed layer of illite and smectite), illite, chlorite, and kaolinite co-existed. Whereas the clay minerals with this ratio did not demonstrate better adsorption capacities for Cd and Pb due to the Cd percentage of the residual fraction being less than 9%. The result of negative correlation between exchangeable Cd and clay minerals implies that illite, chlorite, and kaolinite may preferentially adsorb Cd and Pb. It is similar to the relationship between Cd and Pb in wheat grain and illite, chlorite, and kaolinite. In addition, the health assessment result show that the negative correlation between clay minerals and the noncarcinogenic hazard quotient (HQ) and indicate that clay minerals could reduce the noncarcinogenic risk of Pb and Cd for children. Our findings provide a potential mechanism and application of clay minerals for the remediation of soil contaminated with TMs.

Arsenic-contaminated soil remediation with hyperthermophilic compost: Effects on arsenic bioavailability, soil fertility and bacterial community

Soil arsenic (As) contamination has posed a significant global environmental challenge seriously threatening human health. Compost has attracted broad interests as a kind of eco-friendly and versatile amendment. However, hyperthermophilic compost (HTC), which is newly-developed and more advantageous to environment, has not yet been widely utilized to remediate As-contaminated soil, and its effectiveness remains unclear. Herein, the effects of HTC amendment on soil fertility, As bioavailability, plant growth and soil bacterial community were investigated. After amended with HTC, soil nutrient content and enzyme activity were improved. Concurrently, the content of both total As and available As in soil was reduced, partially due to the formation of organo-As complex with the presence of humic acid and fulvic acid in HTC. Notably, Chinese white cabbage (Brassica campestris L. ssp. chinensis Makino) cultivated in HTC-treated soil exhibited better growth and less As uptake, but showed enhanced translocation of As from the below-ground part to the above-ground part. In particular, the lowest HTC addition ratio (HTC:Soil = 1:10, v:v) proved to be the most optimal, increasing the height, width and biomass of Chinese white cabbage from 9.92 ± 0.72 cm, 6.76 ± 0.31 cm and 4.43 ± 0.49 g, to 21.29 ± 0.48 cm, 19.3 ± 1.44 cm and 23.27 ± 2.45 g, respectively. The results of soil bacterial community analysis revealed that HTC amendment stimulated the growth and metabolism of soil microbes, augmenting the richness and diversity of bacteria related to the methylation and volatilization of As and plant growth. This work suggests that HTC can serve as an effective amendment for As-contaminated soil remediation, and a superior alternative to compound fertilizer for plant cultivation, displaying promising potential for agricultural applications.

Optimizing the management of aerobic composting for antibiotic resistance genes elimination: A review of future strategy for livestock manure resource utilization

Aerobic composting technology is an efficient, safe and practical method to reduce the residues of antibiotics and antibiotic resistance genes (ARGs) due to unreasonable disposal of livestock manure. Nowadays, it remains unclear how aerobic composting works to minimize the level of remaining antibiotics and ARGs in manure. Moreover, aerobic composting techniques even have the potential to enhance ARGs level. Therefore, this study conducted a literature review on ARGs variation during the composting process to assess the fate, migration, and risk features of antibiotics and ARGs in different livestock manure and compost. The relationship between ARGs reduction and crucial factors (temperature, heavy metal, and microbial community structures) in the composting process was discussed. The merits and limitations of different technologies used in compost was summarized. The effects on ARGs reduction in the aerobic composting process with various strategies was examined. We attempt to provide a fresh and novel viewpoint on the advancement of global aerobic composting technology.

A quantitative review of the effects of biochar application on the reduction of Cu concentration in plant: a meta-analysis

Contamination and toxicity of copper (Cu) in soils are global issues, particularly in regions where Cu-based fungicides are utilized. Elevated Cu concentrations can lead to soil contamination and pose significant risks to the ecosystem, including plant life, wildlife, and human health. The application of biochar has been proposed as a viable strategy to mitigate Cu accumulation in plants. However, there is no quantitative and data-based consensus on the impact of biochar on plant Cu accumulation. In this meta-analysis, 624 data records from 65 published literature were collected and the effects of various factors, including biochar properties, experimental conditions, and soil properties on Cu accumulation in plants, were examined through meta-subgroup analysis and meta-regression models. The results obtained indicate a significant dose-dependent effect of biochar in decreasing Cu concentration in plants by an average of 23.45%. Soils with acidic pH values and medium textures were more conducive for biochar to mitigate Cu accumulation in plant tissues. In addition, manure biochar and green waste biochar were found to be more successful in decreasing Cu concentrations in plants compared to other biochar types. Biochar types with pyrolysis temperatures of > 600 °C and pH values of ≥ 10 resulted in greater decreases in plant Cu concentration. Regarding biochar application, biochar minimum range of 1% in potting experiments and 20 t/ha in field experiments have been recommended to effectively decrease Cu concentration in plants. Overall, these findings provide valuable insights into Cu transfer mitigation through food chain to human bodies and for policymakers to take preventive measures.

Assembly of root-associated bacterial community and soil health in cadmium-contaminated soil affected by nano/bulk-biochar compost associations

Biochar (BC) has been proven effective in promoting the production of safety food in cadmium (Cd)-polluted soil and the impact can be further enhanced through interaction with compost (CM). However, there existed unclear impacts of biochar with varying particle sizes in conjunction with compost on microbiome composition, rhizosphere functions, and soil health. Hence, in this study, two bulk-biochar derived from wood chips and pig manure were fabricated into nano-biochar using a ball-milling method. Subsequently, in a field experiment, the root-associated bacterial community and microbial functions of lettuce were evaluated in respond to Cd-contaminated soil remediated with nano/bulk-BCCM. The results showed that compared to bulk-BCCM, nano-BCCM significantly reduced the Cd concentration in the edible part of lettuce and the available Cd in the soil. Both nano-BCCM and bulk-BCCM strongly influenced the composition of bacterial communities in the four root-associated niches, and enhanced rhizosphere functions involved in nitrogen, phosphorus, and carbon cycling, as well as the relative abundance and biodiversity of keystone modules in rhizosphere soil. Furthermore, soil quality index analysis indicated that nano-BCCM exhibited greater potential than bulk-BCCM in maintaining soil health. The data revealed that nano-BCCM could regulate the Cd concentration in lettuce shoot by promoting microbial biodiversity of keystone modules in soil-root continuum and rhizosphere bacterial functions. These findings suggest that nano-biochar compost associations can be a superior strategy for enhancing microbial functions, maintaining soil health, and ensuring crop production safety in the Cd-contaminated soil compared to the mix of bulk-biochar and compost.

Cenococcum geophilum impedes cadmium toxicity in Pinus massoniana by modulating nitrogen metabolism

Nitrogen (N) is of great significance to the absorption, distribution and detoxification of cadmium (Cd). Ectomycorrhizal fungi (EMF) are able to affect the key processes of plant N uptake to resist Cd stress, while the mechanism is still unclear. Therefore, we explored potential strategies of Cenococcum geophilum (C. geophilum) symbiosis to alleviate Cd stress in Pinus massoniana (P. massoniana) from the perspective of plant N metabolism and soil N transformation. The results showed that inoculation of C. geophilum significantly increased the activities of NR, NiR and GS in the shoots and roots of P. massoniana, thereby promoting the assimilation of NO3- and NH4+ into amino acids. Moreover, C. geophilum promoted soil urease and protease activities, but decreased soil NH4+ content, indicating that C. geophilum might increase plant uptake of soil inorganic N. qRT-PCR results showed that C3 symbiosis significantly up-regulated the expression of genes encoding functions involved in NH4+ uptake (AMT3;1), NO3- uptake (NRT2.1, NRT2.4, NRT2.9), as well as Cd resistance (ABCC1 and ABCC2), meanwhile down-regulated the expression of NRT7.3, Cd transporter genes (HMA2 and NRAMP3) in the roots of P. massoniana seedlings. These results demonstrated that C. geophilum was able to alleviate Cd stress by increasing the absorption and assimilation of inorganic N in plants and inhibiting the transport of Cd from roots to shoots, which provided new insights into how EMF improved host resistance to abiotic stress.

Copper pyrazole addition regulates soil mineral nitrogen turnover by mediating microbial traits

The huge amount of urea applied has necessitated best-developed practices to slow down the release of nitrogen (N) fertilizer while minimizing nitrate loss. However, the impact of nitrification inhibitors on mineral-N turnover and the associated microbial mechanisms at different stages remains unknown. A 60-day incubation experiment was conducted with four treatments: no fertilizer (CK), urea (U), urea with copper pyrazole (UC), and urea coated with copper pyrazole (SUC), to evaluate the changes about soil ammonia N (N H 4 + -N) and nitrate N ( NO 3 - -N) levels as well as in soil microbial community throughout the whole incubation period. The results showed that copper pyrazole exhibited significantly higher inhibition rates on urease compared to other metal-pyrazole coordination compounds. The soilN H 4 + -N content peaked on the 10th day and was significantly greater in UC compared to U, while the NO 3 - -N content was significantly greater in U compared to UC on the 60th day. Copper pyrazole mainly decreased the expression of nitrifying (AOB-amoA) and denitrifying (nirK) genes, impacting the soil microbial community. Co-occurrence network suggested that Mycobacterium and Cronobacter sakazakii-driven Cluster 4 community potentially affected the nitrification process in the initial phase, convertingN H 4 + -N to NO 3 - -N. Fusarium-driven Cluster 3 community likely facilitated the denitrification of NO 3 - -N and caused N loss to the atmosphere in the late stage. The application of copper pyrazole may influence the process of nitrification and denitrification by regulating soil microbial traits (module community and functional genes). Our research indicates that the addition of copper pyrazole alters the community function driven by keystone taxa, altering mineral-N turnover and supporting the use of nitrification inhibitors in sustainable agriculture.

Enhanced immobilization of cadmium and lead in contaminated soil using calcium alginate-modified HAP biochar: Improvements in soil health and microbial diversity

A novel adsorbent, calcium alginate-modified HAP (Hydroxyapatite)-wood ear mushroom sticks biochar (CA-HAPMB), was synthesized to enhance the immobilization of Cd and Pb in soil. Over 150 days, applying CA-HAPMB at concentrations of 0%-3% in contaminated soils from Chenzhou City in Hunan Province (CZ) and Shenyang City in Liaoning Province (SY) resulted in decreased effective concentrations of Cd and Pb. Specifically, in CZ soil, Cd and Pb decreased by 30.9%-69.3% and 31.9%-78.6%, respectively, while in SY soil, they decreased by 27.5%-53.7% and 26.4%-62.3%, respectively. Characterization results, obtained after separating CA-HAPMB from the soil, indicate that complexation, co-precipitation, and ion exchange play crucial roles in the efficient immobilization of Cd and Pb by CA-HAPMB. Additionally, adjusting the amount of CA-HAPMB added allows modulation of soil pH, leading to increased soil organic matter and nutrient content. Following treatment with CA-HAPMB for immobilizing Cd and Pb, soil bacteria abundance and diversity increased, further promoting heavy-metal immobilization.

Unveiling biochar potential to promote safe crop production in toxic metal(loid) contaminated soil: A meta-analysis

Biochar application emerges as a promising and sustainable solution for the remediation of soils contaminated with potentially toxic metal (loid)s (PTMs), yet its potential to reduce PTM accumulation in crops remains to be fully elucidated. In our study, a hierarchical meta-analysis based on 276 research articles was conducted to quantify the effects of biochar application on crop growth and PTM accumulation. Meanwhile, a machine learning approach was developed to identify the major contributing features. Our findings revealed that biochar application significantly enhanced crop growth, and reduced PTM concentrations in crop tissues, showing a decrease trend of grains (36.1%, 33.6-38.6%) > shoots (31.1%, 29.3-32.8%) > roots (27.5%, 25.7-29.2%). Furthermore, biochar modifications were found to amplify its remediation potential in PTM-contaminated soils. Biochar application was observed to provide favorable conditions for reducing PTM uptake by crops, primarily through decreasing available PTM concentrations and improving overall soil quality. Employing machine learning techniques, we identified biochar properties, such as surface area and C content as a key factor in decreasing PTM bioavailability in soil-crop systems. Furthermore, our study indicated that biochar application could reduce probabilistic health risks associated with of the presence of PTMs in crop grains, thereby contributing to human health protection. These findings highlighted the essential role of biochar in remediating PTM-contaminated lands and offered guidelines for enhancing safe crop production.

Full-chain analysis on emerging contaminants in soil: Source, migration and remediation

Emerging contaminants (ECs) are gaining attention due to their prevalence and potential negative impacts on the environment and human health. This paper provides a comprehensive review of the status and trends of soil pollution caused by ECs, focusing on their sources, migration pathways, and environmental implications. Significant ECs, including plastics, synthetic polymers, pharmaceuticals, personal care products, plasticizers, and flame retardants, are identified due to their widespread use and toxicity. Their presence in soil is attributed to agricultural activities, urban waste, and wastewater irrigation. The review explores both horizontal and vertical migration pathways, with factors such as soil type, organic matter content, and moisture levels influencing their distribution. Understanding the behavior of ECs in soil is critical to mitigating their long-term risks and developing effective soil remediation strategies. The paper also examines the advantages and disadvantages of in situ and ex situ treatment approaches for ECs, highlighting optimal physical, chemical, and biological treatment conditions. These findings provide a fundamental basis for addressing the challenges and governance of soil pollution induced by ECs.

Nano-selenium and compost vitalized morpho-physio-biochemical, antioxidants and osmolytes adjustment in soybean under tannery effluent polluted soil

The aim of this work was to investigate the impact of nano selenium (N-Se) and compost on the growth, photosynthesis, enzymes activity, compatible solutes and metals accumulation in soybean grown under tannery effluent polluted soil. The plants were exposed to compost application (no compost and compost addition) and foliar application of N-Se (0, 25, 50, and 75 mg L-1). The results showed the addition of compost in soil and foliar applied N-Se alleviated the toxic effect of tannery effluent polluted soil. Furthermore, foliar application of N-Se with basal compost supply significantly improved antoxidant enzymes activity in soybean grown in tannery effluent polluted soil. Addition of compost increased the root dry weight (46.43%) and shoot dry weight (33.50 %), relative water contents by (13.74 %), soluble sugars (15.99 %), stomatal conductance (gs) (83.33 %), intercellular CO2 concentration (Ci) (23.34 %), transpiration rate (E) (12.10 %) and decreased the electrolyte leakage (27.96 %) and proline contents by (20.34 %). The foliage application of N-Se at the rate of 75 mg L-1 showed the most promising results in control and compost amended tannery effluent polluted soil. The determined health risk index (HRI) values were recorded less than 1 for both adults and children under the application of compost and N-Se. In summary, the combined use of N-Se at 75 mg L⁻1 and basal supply of compost is an effective strategy for enhancing soybean productivity while minimizing the potential risks of metal accumulation in soybean grains grown in tannery effluent polluted soil.

Functionality of wheat straw-derived biochar enhanced its efficiency for actively capping Cd and Pb in contaminated water and soil matrices: Insights through batch adsorption and flow-through experiments

The impact of functionality of biochar on pressing environmental issue of cadmium (Cd) and lead (Pb) co-contamination in simultaneous soil and water systems has not sufficiently reported. This study investigated the impact of Fe- and Mg-functionalized wheat straw biochar (Fe-WSBC and Mg-WSBC) on Cd and Pb adsorption/immobilization through batch sorption and column leaching trials. Importantly, Fe-WSBC was more effective in adsorbing Cd and Pb (82.84 and 111.24 mg g-1), regeneration ability (removal efficiency 94.32 and 92.365), and competitive ability under competing cations (83.15 and 84.36%) compared to other materials (WSBC and Mg-WSBC). The practical feasibility of Fe-WSBC for spiked river water verified the 92.57% removal of Cd and 85.73% for Pb in 50 mg L-1 and 100 mg L-1 contamination, respectively. Besides, the leaching of Cd and Pb with Fe-WSBC under flow-through conditions was lowered to (0.326 and 17.62 mg L-1), respectively as compared to control (CK) (0.836 and 40.40 mg L-1). In short, this study presents the applicable approach for simultaneous remediation of contaminated water and soil matrices, offering insights into environmentally friendly green remediation strategies for heavy metals co-contaminated matrices.

Sb/As immobilization and soil function improvement under the combined remediation strategy of modified biochar and Sb-oxidizing bacteria at a smelting site

Antimony (Sb) and arsenic (As) lead to soil pollution and structural degradation at Sb smelting sites. However, most sites focus solely on Sb/As immobilization, neglecting the restoration of soil functionality. Here, we investigated the effectiveness of Fe/H2O2 modified biochar (Fe@H2O2-BC) and Sb-oxidizing bacteria (Bacillus sp. S3) in immobilizing Sb/As and enhancing soil functional resilience at an Sb smelting site. Over a twelve-month period, the leaching toxicity of As and Sb was reduced to 0.05 and 0.005 mg L-1 (GB3838-2002) respectively, with 1% (w/w) Fe@H2O2-BC and 2% (v/v) Bacillus sp. S3 solution. Compared to CK, the combination of Fe@H2O2-BC and Bacillus sp. S3 significantly reduced the bioavailable As/Sb by 98.00%/93.52%, whilst increasing residual As and reducible Sb fractions by 210.31% and 96.51%, respectively. The combined application generally improved soil aggregate structure, pore characteristics, and water-holding capacity. Fe@H2O2-BC served as a pH buffer and long-term reservoir of organic carbon, changing the availability of carbon substrates to bacteria. The inoculation of Bacillus sp. S3 facilitated the transformation of Sb(III)/As(III) to Sb(V)/As(V) and differentiated the composition and functional roles of bacterial communities in soils. The combination increased the abundance of soil saprotrophs by 164.20%, whilst improving the relative abundance of N- and S-cycling bacteria according to FUNGuild and FAPROTAX analysis. These results revealed that the integrated application was instrumental in As/Sb detoxification/immobilization and soil function restoration, which demonstrating a promising microbially-driven ecological restoration strategy at Sb smelting sites.

Green titanium dioxide (TiO2) nanoparticles assisted biodegradation of anthracene employing Serratia quinivorans HP5

The anthracene biodegradation potential of Serratia quinivorans HP5 was studied under a controlled laboratory environment. The green TiO2 nanoparticles (NPs) synthesized from Paenibacillus sp. HD1PAH was used to accelerate the biodegradation process. The synergistic application of TiO2 NPs and S. quinivorans HP5 resulted in a reduction of anthracene concentration by 1.2 folds in liquid-medium and 1.5 folds in contaminated soil. Gas-chromatography and mass-spectrometric investigation showed the production of four anthracene derivatives, namely 1,2-anthracene dihydrodiol, 6,7-benzocoumarin, anthrone, and 9,10-anthraquinoneat the termination of experimental periods. Furthermore, bacterial biomass increased by 23.3 folds in the presence of TiO2 NPs, and overall soil enzyme activities were enhanced by 4.2 folds in the treated samples. In addition, there was a negative correlation observed between the biomass of S. quinivorans HP5 and the concentrations of anthracene, suggesting the involvement of bacterium in anthracene biodegradation processes. The degradation pathway of anthracene revealed its transformation into the less toxic compound 9,10-anthraquinone. Overall, this study elucidates a novel biodegradation pathway for anthracene and highlights the potential of nano-assisted bacterial remediation as a promising approach for environmental cleanup.

The Easily Overlooked Effect of Global Warming: Diffusion of Heavy Metals

Since industrialization, global temperatures have continued to rise. Human activities have resulted in heavy metals being freed from their original, fixed locations. Because of global warming, glaciers are melting, carbon dioxide concentrations are increasing, weather patterns are shifting, and various environmental forces are at play, resulting in the movement of heavy metals and alteration of their forms. In this general context, the impact of heavy metals on ecosystems and organisms has changed accordingly. For most ecosystems, the levels of heavy metals are on the rise, and this rise can have a negative impact on the ecosystem as a whole. Numerous studies have been conducted to analyze the combined impacts of climate change and heavy metals. However, the summary of the current studies is not perfect. Therefore, this review discusses how heavy metals affect ecosystems during the process of climate change from multiple perspectives, providing some references for addressing the impact of climate warming on environmental heavy metals.

Performance of wood waste biochar and food waste compost in a pilot-scale sustainable drainage system for stormwater treatment

Sustainable drainage system (SuDS) for stormwater reclamation has the potential to alleviate the water scarcity and environmental pollution issues. Laboratory studies have demonstrated that the capacity of SuDS to treat stormwater can be improved by integrating biochar and compost in the filter media, whereas their performance in scaled-up applications is less reported. This study examines the effectiveness of a pilot-scale SuDS, bioswale followed by bioretention, amended with wood waste biochar (1, 2, and 4 wt.%) and food waste compost (2 and 4 wt.%) to simultaneously remove multiple pollutants including nutrients, heavy metals, and trace organics from the simulated stormwater. Our results confirmed that SuDS modified with both biochar (2 wt.%) and compost (2 wt.%) displayed superior water quality improvement. The system exhibited high removal efficiency (> 70%) for total phosphorus and major metal species including Ni, Pb, Cd, Cr, Cu, and Zn. Total suspended solids concentration was approaching the detection limit in the effluent, thereby confirming its capability to reduce turbidity and particle-associated pollutants from stormwater. Co-application of biochar and compost also moderately immobilized trace organic contaminants such as 2,4-dichlorophenoxyacetic acid, diuron, and atrazine at field-relevant concentrations. Moreover, the soil amendments amplified the activities of enzymes including β-D-cellobiosidase and urease, suggesting that the improved soil conditions and health of microbial communities could possibly increase phyto and bioremediation of contaminants accumulated in the filter media. Overall, our pilot-scale demonstration confirmed that the co-application of biochar and compost in SuDS can provide a variety of benefits for soil/plant health and water quality.

Electrochemical Impedance Spectroscopy for the Sensing of the Kinetic Parameters of Engineered Enzymes

The study presents a promising approach to enzymatic kinetics using Electrochemical Impedance Spectroscopy (EIS) to assess fundamental parameters of modified enteropeptidases. Traditional methods for determining these parameters, while effective, often lack versatility and convenience, especially under varying environmental conditions. The use of EIS provides a novel approach that overcomes these limitations. The enteropeptidase underwent genetic modification through the introduction of single amino acid modifications to assess their effect on enzyme kinetics. However, according to the one-sample t-test results, the difference between the engineered enzymes and hEKL was not statistically significant by conventional criteria. The kinetic parameters were analyzed using fluorescence spectroscopy and EIS, which was found to be an effective tool for the real-time measurement of enzyme kinetics. The results obtained through EIS were not significantly different from those obtained through traditional fluorescence spectroscopy methods (p value >> 0.05). The study validates the use of EIS for measuring enzyme kinetics and provides insight into the effects of specific amino acid changes on enteropeptidase function. These findings have potential applications in biotechnology and biochemical research, suggesting a new method for rapidly assessing enzymatic activity.

Silicon nanoparticles vs trace elements toxicity: Modus operandi and its omics bases

Phytotoxicity of trace elements (commonly misunderstood as 'heavy metals') includes impairment of functional groups of enzymes, photo-assembly, redox homeostasis, and nutrient status in higher plants. Silicon nanoparticles (SiNPs) can ameliorate trace element toxicity. We discuss SiNPs response against several essential (such as Cu, Ni, Mn, Mo, and Zn) and non-essential (including Cd, Pb, Hg, Al, Cr, Sb, Se, and As) trace elements. SiNPs hinder root uptake and transport of trace elements as the first line of defence. SiNPs charge plant antioxidant defence against trace elements-induced oxidative stress. The enrolment of SiNPs in gene expressions was also noticed on many occasions. These genes are associated with several anatomical and physiological phenomena, such as cell wall composition, photosynthesis, and metal uptake and transport. On this note, we dedicate the later sections of this review to support an enhanced understanding of SiNPs influence on the metabolomic, proteomic, and genomic profile of plants under trace elements toxicity.

The role of afforestation with diverse woody species in enhancing and restructuring the soil microenvironment in polymetallic coal gangue dumps

To elucidate the effects of long-term (20 years) afforestation with different woody plant species on the soil microenvironment in coal gangue polymetallic contaminated areas. This study analyzed the soil physicochemical properties, soil enzyme activities, soil ionophore, bacterial community structure, soil metabolite, and their interaction relationships at different vertical depths. Urease, sucrase, and acid phosphatase activities in the shallow soil layers increased by 4.70-7.45, 3.83-7.64, and 3.27-4.85 times, respectively, after the restoration by the four arboreal plant species compared to the plant-free control soil. Additionally, it reduced the content of available elements in the soil and alleviated the toxicity stress for Cd, Ni, Co, Cr, As, Fe, Cu, U, and Pb. After the long-term restoration of arboreal plants, the richness and Shannon indices of soil bacteria significantly increased by 4.77-23.81% and 2.93-7.93%, respectively, broadening the bacterial ecological niche. The bacterial community structure shaped by different arboreal plants exhibited high similarity, but the community similarity decreased with increasing vertical depth. Soils Zn, U, Sr, S, P, Mg, K, Fe, Cu, Ca, Ba, and pH were identified as important influencing factors for the community structure of Sphingomonas, Pseudarthrobacter, Nocardioides, and Thiobacillus. The metabolites such as sucrose, raffinose, L-valine, D-fructose 2, 6-bisphosphate, and oxoglutaric acid were found to have the greatest effect on the bacterial community in the rhizosphere soils for arboreal plants. The results of the study demonstrated that long-term planting for woody plants in gangue dumps could regulate microbial abundance and symbiotic patterns through the accumulation of rhizosphere metabolites in the soil, increase soil enzyme activity, reduce heavy metal levels, and improve the soil environment in coal gangue dumps.

Efficient stabilization of arsenic migration and conversion in soil with surfactant-modified iron-manganese oxide: Environmental effects and mechanistic insights

The use of iron-manganese oxide (FMO) as a promising amendment for remediating arsenic (As) contamination in soils has gained attention, but its application is limited owing to agglomeration issues. This study aims to address agglomeration using surfactant-modified FMO and investigate their stabilization behavior towards As and resulting environmental changes upon amendments. The results confirmed the efficacy of surfactants and demonstrated that cetyltrimethylammonium-bromide-modified FMO significantly reduced the leaching concentration of As by 92.5 % and effectively suppressed the uptake of As by 85.8 % compared with the control groups. The ratio of the residual fraction increased from 30.5-41.6 % in unamended soil to 67.9-69.2 %. The number of active sites was through the introduction of surfactants and immobilized As via complexation, ion exchange, and redox reactions. The study also revealed that amendments and the concentration of As influenced the soil physicochemical properties and enriched bacteria associated with As and Fe reduction and changed the distribution of C, N, Fe, and As metabolism genes, which promoted the stabilization of As. The interactions among cetyltrimethylammonium bromide, FMO, and microorganisms were found to have the greatest effect on As immobilization.

Distribution of nitrate/nitrite and toxic metals in the soil-potato system and its health risk assessment in Iran

Potato is one of the essential food products whose health quality is greatly influenced by soil contamination and properties. In the current study, we have investigated the physicochemical characteristics of agricultural areas and the accumulation of nitrite/nitrate and metals in potato products in Hamedan, Iran. After determining the physicochemical characteristics of soil samples from four agricultural regions of Hamedan, 48 potato samples were collected from these regions. The heavy metals and nitrate/nitrite content were determined by ICP-OES and calorimetric methods, respectively. A negative correlation was observed between soil pH changes with nitrite/nitrate content and the accumulation of some heavy elements in potatoes. Furthermore, a positive correlation was found between soil phosphorus content and lead accumulation in potato. In present study, the amounts of lead, nitrate, and nitrite in 83.3%, 56%, and 12% of the collected samples were higher than the permissible limit reported by the World Health Organization (WHO), respectively. The EDI range for nitrate and nitrite was determined to be 130-260 and 1.4-2.7 µg/kg/day, respectively, which is much lower than the RfD set by the US Environmental Protection Agency (USEPA) for nitrite and nitrate. Among metal pollutants, the toxic risk caused by lead in potato consumers was higher than the threshold limit. In conclusion, our findings showed that the physicochemical characteristics of the soil could effectively increase the availability of metal pollutants and nitrite/nitrate to the potato product and significantly reduce its health quality. Therefore, monitoring these pollutants in the soil-potato system, preventing the entry of industrial wastewater, and managing the use of agricultural fertilizers can effectively improve the health of this product for consumers.

Substation of vermicompost mitigates Cd toxicity, improves rice yields and restores bacterial community in a Cd-contaminated soil in Southern China

Cadmium (Cd) contamination in agricultural soil is a global concern for soil health and food sustainability because it can cause Cd accumulation in cereal grains. An in-situ stabilizing technology (using organic amendments) has been widely used for Cd remediation in arable lands. Therefore, the current study examined the influence of vermicompost (VC) on soil biochemical traits, bacterial community diversity and composition, Cd uptake and accumulation in rice plants and grain yield in a Cd-contaminated soil during the late growing season in 2022. Different doses of VC (i.e., V1 = 0 t ha-1, V2 = 3 t ha-1 and V3 = 6 t ha-1) and two concentrations of Cd (i.e., Cd1 = 0 and Cd2 = 50 mg Cd Kg-1 were used. We performed high-throughput sequencing of 16S ribosomal RNA gene amplicons to characterize soil bacterial communities. The addition of VC considerably affected the diversity and composition of the soil bacterial community; and increased the relative abundance of phyla Chloroflexi, Proteobacteria, Acidobacteriota, Plantomycetota, Gemmatimonadota, Patescibacteria and Firmicute. In addition, VC application, particularly High VC treatment, exhibited the highest bacterial diversity and richness (i.e., Simpson, Shannon, ACE, and Chao 1 indexes) of all treatments. Similarly, the VC application increased the soil chemical traits, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), total potassium (TK), total phosphorous (TP) and enzyme activities (i.e., acid phosphatase, catalase, urease and invertase) compared to non-VC treated soil under Cd stress. The average increase in SOC, TN, AN, TK and TP were 5.75%, 41.15%, 18.51%, 12.31%, 25.45% and 29.67%, respectively, in the High VC treatment (Pos-Cd + VC3) compared with Cd stressed soil. Redundancy analysis revealed that the leading bacterial phyla were associated with SOC, AN, TN, TP and pH, although the relative abundance of Firmicutes, Proteobacteria, Bacteroidata, and Acidobacteria on a phylum basis and Actinobacteria, Gammaproteobacteria and Myxococcia on a class basis, were highly correlated with soil environmental factors. Moreover, the VC application counteracted the adverse effects of Cd on plants and significantly reduced the Cd uptake and accumulation in rice organs, such as roots, stem + leaves and grain under Cd stress conditions. Similarly, applying VC significantly increased the fragrant rice grain yield and yield traits under Cd toxicity. The correlation analysis showed that the increased soil quantities traits were crucial in obtaining high rice grain yield. Generally, the findings of this research demonstrate that the application of VC in paddy fields could be useful for growers in Southern China by sustainably enhancing soil functionality and crop production.

Greenhouse gas emission characteristics and influencing factors of agricultural waste composting process: A review

China, being a major agricultural nation, employs aerobic composting as an efficient approach to handle agricultural solid waste. Nevertheless, the composting process is often accompanied by greenhouse gas emissions, which are known contributors to global warming. Therefore, it is urgent to control the formation and emission of greenhouse gases from composting. This study provides a comprehensive analysis of the mechanisms underlying the production of nitrous oxide, methane, and carbon dioxide during the composting process of agricultural wastes. Additionally, it proposes an overview of the variables that affect greenhouse gas emissions, including the types of agricultural wastes (straw, livestock manure), the specifications for compost (pile size, aeration). The key factors of greenhouse gas emissions during composting process like physicochemical parameters, additives, and specific composting techniques (reuse of mature compost products, ultra-high-temperature composting, and electric-field-assisted composting) are summarized. Finally, it suggests directions and perspectives for future research. This study establishes a theoretical foundation for achieving carbon neutrality and promoting environmentally-friendly composting practices.

Effect of montmorillonite modified straw biochar on transfer behavior of lead and copper in the historical mining areas of dry-hot valleys

Due to the rapid development of human beings, heavy metals are occurred in the Yunnan-Guizhou Plateau and Panxi Plateau, the special dry and hot climate areas. Pb and Cu can be quickly transferred through water-plant-animal, further harm to human health by food chain. Therefore, the study of heavy metal treatment is imminent. In this study, Biochar-montmorillonite composites were prepared by co-pyrolysis and characterized, and their ability to remove lead and copper from water-soil process were tracked. And their effectiveness in remediating soil contaminated by lead and copper was documented. The composite material has the rich pore structure, large specific surface area (81.5 m2/g) and a variety of surface functional groups such as C-C, CO, ester-metal and metal-oxygen bonds. Pb and Cu can be effectively adsorbed and fixed to the level of no harm to human health. The adsorption reaction of lead and copper on the Biochar-montmorillonite composites is more suitable to be described by Langmuir adsorption and pseudo-second-order kinetics models. The saturation adsorption capacity of the composite for Pb was measured as 212.5 mg/g. For Cu, it was 136.5 mg/g. The data were fitted by a two-compartment first-order kinetic model. ffast for Pb and Cu is estimated to be 0.81 and 0.78, respective. Fast adsorption is dominant and belongs to typical chemical adsorption, which is consistent with the second-order kinetic results. With 5 % of the composite, approximately 80 % of exchangeable heavy metals in those soils collected from the Yunnan-Guizhou Plateau and Panxi Plateau were reduced. The biochar-montmorillonite composites made Pb and Cu change to stable residual state, up to 35 %. Besides, it effectively restored the activity of urease and sucrase in soils. Results indicated that biochar-montmorillonite composites can be effectively used as an environment-friendly adsorbent or passivator to purify heavy metals in soils.

Interactive mode of biochar-based silicon and iron nanoparticles mitigated Cd-toxicity in maize

Cadmium contamination poses severe environmental and health threats, necessitating effective mitigation strategies. Rice husk biochar (BC) and nanoparticle (NP) treatments are emerging strategies with limited research on their synergistic benefits. This study assesses BC, silicon NPs (nSi), and iron NPs (nFe) modifications (B-nSi, B-nFe, and B-nSi-nFe) to reduce Cd-bioavailability in soil and its toxicity in maize, not reported before. Characterization of amendments validated, nSi and nFe attachment to BC, forming new mineral crystals to adsorb Cd. We found that B-nSi-nFe induced Cd-immobilization in soil by the formation of Cd-ligand complexes with the effective retention of NPs within microporous structure of BC. B-nSi-nFe increased soil pH by 0.76 units while reducing bioavailable Cd by 49 %, than Ck-Cd. Resultantly, B-nSi-nFe reduced Cd concentrations in roots and shoots by 51 % and 75 %, respectively. Moreover, the application of B-nSi-nFe significantly enhanced plant biomass, antioxidant activities, and upregulated the expression of antioxidant genes [ZmAPX (3.28 FC), ZmCAT (3.20 FC), ZmPOD (2.58 FC), ZmSOD (3.08 FC), ZmGSH (3.17 FC), and ZmMDHAR (3.80 FC)] while downregulating Cd transporter genes [ZmNramp5 (3.65 FC), ZmHMA2 (2.92 FC), and ZmHMA3 (3.40 FC)] compared to Ck-Cd. Additionally, confocal microscopy confirmed the efficacy of B-nSi-nFe in maintaining cell integrity due to reduced oxidative stress. SEM and TEM observations revealed alleviation of Cd toxicity to stomata, guard cells, and ultracellular structures with B-nSi-nFe treatment. Overall, this study demonstrated the potential of B-nSi-nFe for reducing Cd mobility in soil-plant system, mitigating Cd-toxicity in plants and improving enzymatic activities in soil.

Composting municipal solid waste and animal manure in response to the current fertilizer crisis - a recent review

The dynamic price increases of fertilizers and the generation of organic waste are currently global issues. The growth of the population has led to increased production of solid municipal waste and a higher demand for food. Food production is inherently related to agriculture and, to achieve higher yields, it is necessary to replenish the soil with essential minerals. A synergistic approach that addresses both problems is the implementation of the composting process, which aligns with the principles of a circular economy. Food waste, green waste, paper waste, cardboard waste, and animal manure are promising feedstock materials for the extraction of valuable compounds. This review discusses key factors that influence the composting process and compares them with the input materials' parameters. It also considers methods for optimizing the process, such as the use of biochar and inoculation, which result in the production of the final product in a significantly shorter time and at lower financial costs. The applications of composts produced from various materials are described along with associated risks. In addition, innovative composting technologies are presented.

Using Fe/H2O2-modified biochar to realize field-scale Sb/As stabilization and soil structure improvement in an Sb smelting site

Antimony (Sb) and arsenic (As) released from the Sb smelting activities pose a major environmental risk and ecological degradation in Sb smelting sites. Here the effects of Fe/H2O2 modified biochar (Fe@H2O2-BC) on the synchronous stabilization of Sb/As and the improvement of soil structure in a typical Sb smelting site in Southern China based on a 1-year field experiment were studied. Application of ≥1 % (w/w) Fe@H2O2-BC could stably decrease the leaching concentrations of Sb and As of the polluted soils to Environmental quality standards for surface water Chinese Level III (GB3838-2002). Compared to the untreated soils, the stabilization efficiency of soil Sb and As treated by Fe@H2O2-BC reached 90.7 % ~ 95.7 % and 89.6 % ~ 90.8 %, respectively. The residue fractions of Sb/As in the soils increased obviously, and the bio-availability of Sb/As decreased by 65.0-95.6 % and 91.1-96.0 %, respectively. Moreover, Fe@H2O2-BC addition elevated soil organic carbon content, increased soil porosity, and improved water retention capacity, indicating the positive effects on soil structure and functions. Advanced mineral identification and characterization systems showed that Sb/As usually occurred in Fe-bearing minerals and stabilized by surface complexation and co-precipitation. The findings demonstrated that 1 % (w/w) Fe@H2O2-BC was appropriate to Sb/As stabilization and soil function recovery following field conditions, which provided potential application for ecological restoration in Sb smelting sites.

Effect of biochar with various pore characteristics on heavy metal passivation and microbiota development during pig manure composting

Understanding the porosity of biochar (BC) that promotes the heavy metal (HM) passivation during composting can contribute to the sustainable management of pig manure (PM). The current work aimed to explore the influence of BC with varying pore sizes on the physicochemical properties and morphological changes of HMs (including Zn, Cu, Cr, As, and Hg), and microbiota development during PM composting. The various pore sizes of BC were generated by pyrolyzing pine wood at 400 (T1), 500 (T2), 600 (T3) and 700 (T4) °C, respectively. The results revealed a positive correlation between specific surface area of BC and pyrolysis temperature. BC addition contributed to a significantly extended compost warming rate and duration of high-temperature period, as well as HM passivation, reflected in the decrease in Exc-Zn (63-34%) and Red-Cu (28-13%) content, and the conversion of Oxi-Cr (29-21%) and Red-Hg (16-5%) to more stable forms. Moreover, BC at T4 exhibited the best effect on Zn and Cu passivation due to the highest specific surface area (380.03 m2/g). In addition to its impact on HM passivation, BC addition improved the microbial environment during PM composting, leading to enhanced microbial diversity and richness. Notably, Chloroflexi and Bacteroidota played key roles in promoting the transformation of Exc-Cu and Red-Hg into stable forms. This phenomenon further stimulated the enhanced decomposition of organic matter (OM) when BC prepared at 600-700 °C was added. Therefore, it can be concluded that the regulation of BC porosity is an effective strategy to improve HM passivation and the overall effectiveness of PM composting.

Enhanced Cd activation by Coprinus comatus endophyte Bacillus thuringiensis and the molecular mechanism

Fungal endophytes not only tolerate and activate Cd in soil but also promote host growth, yet its Cd activation capacity and mechanism remain unrevealed. Our previous study isolated a robust endophyte Bacillus thuringiensis L1 from Coprinus comatus fruiting body with splendid Cd resistance and activation abilities under laboratory conditions. In this study, those peculiarities were investigated in the actual soil environment. L1 could significantly increase the soil bioavailable Cd content and effectively compensate for alkali-hydro nitrogen losses and microbial inhibition caused by Cd. Furthermore, L1 inoculation improved the soil's bacterial community structure and increased the relative abundance of Cd-resistant bacteria, such as Actinobacteria, Chloroflexi, Acidobacter, and Firmicutes, closely associated with the soil enzyme activity shift. The genome sequencing analysis revealed the presence of genes related to growth promotion, resistance to Cd stress, and Cd activation, which were significantly up-regulated under Cd stress. Notably, L1 mainly activates Cd in soil by secreting citric acid, succinic acid, siderophore, and soluble phosphorus substances to chelate with Cd or dissolve bounded Cd. Meanwhile, the metal-responsive transcription repressor (CadC) and the Cd-translocating protein P-type ATPase (CadA) can help the L1 to suppress the toxicity of Cd. Those results help to unveil the possible mechanism of L1 in Cd-contaminated soil remediation, providing a clear strategy for Cd bio-extraction from soil.

Effects of biochar layer position on treatment performance and microbial community in subsurface flow constructed wetlands for removal of cadmium and lead

Levels of cadmium (Cd) and lead (Pb) correspond to common composition in acid mine wastewater of Hunan Province of China. The removal path of Cd and Pb and the structure of microbial community were investigated by developing constructed wetlands (CWs) with different layer positions of biochar. The biochar as a layer at the bottom of CW (BCW) system exhibited maximum Cd and Pb removal efficiencies of 96.6-98.6% and 97.2-98.9%, respectively. Compared with original soil, BCW increased the relative proportions of Proteobacteria, Firmicutes, Acidobacteriota, Verrucomicrobiota, Desulfobacterota, Armatimonadota, Bacteroidota, Patescibacteria, Basidiomycota (phylum level) and Burkholderia-Caballeronia-Paraburkholderia, Citrifermentans, Chthonomonadales, Cellulomonas, Geothrix, Terracidiphilus, Gallionellaceae, Microbacterium, Vanrija, Apiotrichum, Saitozyma, Fusarium (genus level). The concentrations of Cd and Pb were positively correlated with the abundance of Verrucomicrobiota, Basidiomycota (phylum level), and Methylacidiphilaceae, Meyerozyma, Vanrija (genus level). This study demonstrates that BCW system can improve removal performance toward Cd and Pb, as well as alter microbial community.